Tunnel blasting air shock wave peak forecasting method based on blasting action index

Abstract

According to the tunnel blasting air shock wave peak forecasting method based on the blasting action index, the blasting physics, the blasting shock wave propagation theory, engineering statistical analysis and other principles are comprehensively utilized, the relation between blasting parameters and the shock wave effect is quantitatively described by constructing the blasting action index, and the blasting air shock wave peak forecasting method is established. And rapid and effective prediction and control of the blast air shock wave peak value are realized. The technology can be widely applied to tunnel engineering, mine engineering, urban underground space development and other scenes needing blasting construction so as to guarantee construction safety, optimize blasting design and reduce blasting disturbance influences.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and blasting engineering, and specifically to a method for predicting the peak value of air shock waves in tunnel blasting based on the blasting action index. Background Technology

[0002] In tunnel and underground engineering construction, the drill-and-blast method remains one of the primary construction techniques due to its economic efficiency and applicability. However, the enormous energy released during blasting creates high-temperature, high-pressure explosion products, triggering air shock waves that propagate rapidly within the confined underground space. Excessively high peak pressures of these blast air shock waves not only directly threaten the safety of personnel and equipment on site but also damage unexcavated rock masses, support structures, and adjacent buildings, potentially leading to safety accidents. Therefore, accurately predicting the peak pressure of the air shock waves is a crucial prerequisite for optimizing blasting design parameters, controlling the range of harmful blasting effects, and ensuring construction safety.

[0003] Currently, the methods for predicting the peak pressure of shock waves can be mainly divided into the following three categories: 1) Empirical Formula Method: Formulas fitted based on test data under specific working conditions (such as those in the "Blasting Safety Regulations") are simple in form and quick to calculate. However, they typically only consider the total charge (Q) and the distance between measuring points (R) as the main variables, severely neglecting the significant constraints of blasting parameter arrangements (such as the minimum resistance line L) on the direction of explosion energy release, shock wave propagation path, and energy dissipation. This leads to a significant decrease in prediction accuracy and limited applicability when applied to tunnels with different cross-sectional shapes, sizes, or charge arrangements.

[0004] 2) Numerical simulation method: It can simulate the propagation process of shock waves in complex geometric spaces with relatively high accuracy. However, its main drawbacks are complex modeling, long calculation time, and high requirements for computing resources, making it difficult to meet the timeliness requirements of rapid prediction and scheme optimization on construction sites.

[0005] 3) Physical test method: The results are intuitive and reliable, but the cost is high, the cycle is long, the implementation is complicated, and it is difficult to cover all working conditions. It is mainly used for key verification or theoretical research and is difficult to use as a routine prediction method.

[0006] In existing technologies, invention patent CN110008603A primarily focuses on evaluating the attenuation effect of the mouth structure on the generated shock wave, rather than predicting the initial peak pressure at the blast source. Patent CN116772670A emphasizes deducing the safe distance based on safety standards; its core lies in distance determination rather than the accurate prediction of the peak pressure itself. Patent CN104315934A focuses on physical protection devices and methods for shock waves, falling under the category of "prevention," and makes limited contributions to predictive models.

[0007] In summary, the fundamental flaw of existing technologies, especially the widely used empirical formula method, lies in its failure to fully consider the decisive influence of key geometric constraints on the release of blast energy (particularly the minimum resistance line L) on the peak pressure of the air shock wave. This results in existing prediction models generally exhibiting insufficient accuracy and poor applicability under complex and variable tunnel blasting conditions. There is an urgent need to develop a simple and reliable prediction method that can effectively integrate explosive parameters, spatial geometric constraints, and energy release characteristics. Summary of the Invention

[0008] The purpose of this invention is to provide a method for predicting the peak value of air shock waves from tunnel blasting based on a blasting action index. This method comprehensively utilizes principles of blasting physics, blast shock wave propagation theory, and engineering statistical analysis. By constructing a blasting action index, it quantitatively describes the relationship between blasting parameters and shock wave effects, enabling rapid and effective prediction and control of the peak value of blasting air shock waves. This technology can be widely applied in scenarios requiring blasting construction, such as tunnel engineering, mining engineering, and urban underground space development, to ensure construction safety, optimize blasting design, and reduce the impact of blasting disturbances.

[0009] To achieve the above-mentioned technical features, the objective of this invention is as follows: a method for predicting the peak value of air shock waves in tunnel blasting based on the blasting action index, comprising the following steps: Step 1, Collection of explosive parameters and on-site information: Collect the parameters of the explosives used during the blasting process, and based on the tunnel... Step 2, Determining environmental parameters: Determine the environmental parameters during the blasting process; Step 3, obtaining coefficients: For different tunnel cross sections, different types of explosives, and different burial depths, small-scale field tests are first conducted to calibrate the parameters. Step 4: Construct and validate the blast shock wave prediction model; Step 5: Establish a database of fitting coefficients; Step 6: Model promotion and batch application.

[0010] Preferably, step 1 specifically includes: Step 1.1: Determine the total charge amount for single-stage detonation based on the blasting design. Q ; Step 1.2: Measure or calculate the cross-sectional area of ​​the tunnel in the area to be blasted based on the design drawings; for irregular cross-sections, calculate the equivalent area using the equivalent circle method or numerical integration method. S ; Step 1.3: Measure the linear spatial distance between the measuring point and the geometric center of the detonating charge. R ; Step 1.4: Measure or determine, based on the blasting design drawings, the shortest distance from the center of the explosive charge that contributes the most to the shock wave at the measuring point to the nearest free surface, i.e. L value.

[0011] Preferably, step 2 specifically includes: Step 2.1: Determine the initial air pressure based on altitude. P 0; Step 2.2: Determine the initial air density based on temperature and air pressure. ρ 0.

[0012] Preferably, step 3 specifically includes: Step 3.1: Before each test, set up multiple measuring points at different locations, install pressure sensors, measure and record the actual peak overpressure; Step 3.2, after collecting the actual peak overpressure Δ measured each time... P and the corresponding total charge Q equivalent area S、 Distance of the air shock wave from the explosion source R and minimum resistance line length L Then, according to equation (12) and using these data: Δ P , Q , S, R, L The optimal coefficients are obtained by nonlinear fitting: k , α , η ; (12)

[0013] Preferably, step 4 specifically includes: Step 4.1: First, use the parameters obtained in Step 3 to build a prediction model; Step 4.2 Next, install high-precision pressure sensors at the predicted measurement points or representative locations to simultaneously monitor the peak overpressure of the actual air shock wave generated by the blast. Step 4.3: Next, compare and analyze the model's predicted values ​​with the actual measured values ​​and calculate the relative error. If the prediction error is within an acceptable range, it indicates that the coefficients are applicable and the model is reliable. If the prediction error is large or there is a systematic bias, the parameter acquisition needs to be checked. Q, S, R, L To determine the accuracy, the input parameters are then adjusted based on the analysis results, or the fitting coefficients are iteratively optimized and updated using newly added measured data.

[0014] Preferably, step 5 specifically includes: For common tunnel cross-section types, commonly used explosive types and typical burial depth conditions, a database of fitting coefficients is established in advance through steps 1 to 4. During implementation, the closest coefficient set is retrieved from the database based on the tunnel type and explosive type of the current project.

[0015] Preferably, the common tunnel cross-section types include archway-shaped, circular, and horseshoe-shaped.

[0016] Preferably, step 6 specifically includes: Once verified as reliable, for subsequent sections of the same tunnel or similar cross-sections and blasting designs with similar explosive charges, only new samples need to be collected. Q , S , R With the parameters, the peak value of the shock wave at different locations can be quickly predicted using the calibrated formula (12) and coefficients, without the need for complex modeling or calculation; The fully validated model coefficients k , α , η The scope of application is included in the database, and it can be directly promoted and applied in similar projects, which will greatly improve the efficiency and reliability of safety pre-control of blasting shock waves in similar tunnels.

[0017] Preferably, similar projects include geology, cross-section, explosives, and burial depth.

[0018] The present invention has the following beneficial effects: The present invention provides a method for predicting the peak value of air shock waves from tunnel blasting based on the blasting action index. This method has the following advantages: Based on the dimensional analysis method, this method integrates multiple factors such as explosive parameters, tunnel cross-section size, and borehole depth by constructing a dimensionless blasting action index, and establishes a unified prediction model. It is applicable to the prediction of tunnel blasting shock wave intensity under different tunnel cross-sections and different borehole charge lengths. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 These are the fitting test data for this invention.

[0021] Figure 2 This is a comparison chart of the prediction formula of this invention, the traditional prediction formula, and the measured results.

[0022] Figure 3 The root mean square error is the difference between the prediction results of this invention, the traditional forecast results, and the measured results.

[0023] Figure 4 This is a flowchart illustrating the implementation of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The above technical solutions will be described in detail below with reference to the accompanying drawings and two specific embodiments. It should be understood that the embodiments described herein are only for explanation and illustration of the present invention, and not for limiting the scope of this application.

[0026] Currently, the empirical formula (1) for calculating the overpressure of the explosive air shock wave in the "Safety Regulations for Blasting" GB6722-2014 is as follows: (1) In the formula: Δ P For the overpressure of the explosive air shock wave, 10 5 Pa, Q For the quality of explosives, R This represents the distance from the explosion source.

[0027] The "Implementation Manual for Blasting Safety Regulations" adds another factor to blasting in roadways: the cross-sectional area of ​​the roadway. S Therefore, the empirical formula (2) for the overpressure of the air shock wave in the blasting explosion in the tunnel is obtained. The calculation method is shown in the following formula (2): (2) In the formula: β The surface roughness coefficient of the tunnel. D The equivalent diameter of the tunnel cross-section. R This represents the distance from the explosion source.

[0028] The core flaw of existing empirical formula methods in predicting the peak pressure of air shock waves from tunnel blasting lies in neglecting the crucial geometric constraints (line of minimum resistance) of blast energy release. L To understand the significant impact of shock wave formation and propagation, this invention aims to establish a peak pressure prediction model with clearer physical meaning and wider applicability.

[0029] This invention recognizes that, in enclosed or semi-enclosed tunnel spaces, the efficiency of explosive energy release, the direction and intensity of shock wave propagation, depend not only on the explosive itself (quantity) Q Explosive popularity Q v It is also strongly constrained by its surrounding spatial boundaries (especially the nearest free surface). Minimum resistance line length ( L The distance from the borehole (or explosive charge) to the nearest free surface is a key geometric parameter that determines the effective utilization rate of explosion energy, the expansion direction of explosion products, and the initial intensity and propagation path of the shock wave. (Ignore...) L This is tantamount to ignoring the core constraint mechanism of tunnel space on the release of blasting energy, which is the fundamental reason for the inaccuracy of traditional empirical formulas in prediction.

[0030] To overcome this deficiency, this invention, based on the traditional dimensional analysis framework, creatively incorporates the concept of "minimum resistance line length ( L The "blasting effect index" is introduced as one of the core variables. This constructs a model with the "blasting effect index" as the core predictor, achieving dimensionless modeling under multivariate conditions.

[0031] Dimensional analysis is a method that derives functional relationships between variables based on the fundamental dimensions of physical quantities (mass [M], length [L], time [T], etc.), and is widely used in physical problems involving multivariable coupling. By converting all relevant physical quantities into dimensionless factors, the essential connections between variables can be revealed, the fitting dimensionality can be reduced, and the universality and stability of the prediction model can be improved.

[0032] In the addition of minimum resistance line length ( L After taking the initial pressure of the air shock wave as a variable, the main factors affecting the peak pressure of the air shock wave include: the initial air pressure. P 0 and density ρ 0, the distance of the air shock wave from the explosion source. R Minimum resistance line length L Tunnel cross-sectional area S Explosive energy per unit area of ​​tunnel cross section W The energy of the explosive W It is calculated according to formula (3).

[0033] (3) In the formula: For the explosive heat, For the quality of explosives, This represents the cross-sectional area of ​​the tunnel.

[0034] The mathematical relationships between these physical quantities can be expressed in the following form: (4) Depend on π Theorem, choosing three independent physical quantities Q , P 0, R If we take the unit of as the basic unit, then we can obtain the functional relationship between the four dimensionless quantities from the functional relationship between the above physical quantities, as shown in the following equation (5): (5) According to the principle of dimensionless quantity consistency, dimensionless quantities can be... π , π 1. π 2. π 3 were established separately, among which In the formula a 0、b 0、 c If 0 is an undetermined coefficient, then the following formula (6) can be listed: (6) Equation (7) is obtained by solving the problem: (7) Therefore, we can obtain Similarly, for , , Then, based on the principle of dimensional consistency, we can obtain equation (8): (8) Therefore, the dimensionless functional relationship can be expressed as equation (9): (9) Due to the initial density of air ρ 0. Pressure P 0 and explosive heat Q Since it is a constant, equation (9) can be simplified to equation (10): (10) Based on the formula in the Blasting Safety Regulations Implementation Manual, a modified formula considering the influence of the resistance line is established, as shown in equation (11): (11) Finally, the constant is heated. Q v Hides, about to W Transform into If the form is , then equation (11) can be written as equation (12).

[0035] (12) In the formula: L The minimum resistance line is m; Q The amount of explosive is expressed in kg. R The distance from the explosion source is in meters (m). k , α , η All of these are fitting parameters.

[0036] Example 1: This invention provides a method for predicting the peak value of air shock waves from tunnel blasting based on the blasting action index. For example... Figure 4 As shown, it includes the following steps: Step 1: Explosive parameters and on-site information collection. Determine the total charge amount for single-stage detonation based on the blasting design. QMeasure or calculate the cross-sectional area of ​​the tunnel in the area to be blasted based on the design drawings. For irregular cross-sections, the equivalent area can be calculated using the equivalent circle method or numerical integration method. S ; The linear spatial distance between the measuring point and the geometric center of the detonating charge (group) R ; Measure or determine, based on the blasting design drawings, the shortest distance from the center of the explosive charge that contributes the most to the shock wave at the measuring point to the nearest free surface (free face), i.e. L value.

[0037] Step 2, Determining environmental parameters: Determine the initial air pressure based on altitude. P 0; Determine the initial air density based on temperature and air pressure. ρ 0.

[0038] Step 3, coefficient acquisition: For different tunnel cross-sections, different types of explosives, and different burial depths, small-scale field tests are first conducted to calibrate the parameters. Before each test, multiple measuring points (pressure sensors) are set up at different locations to measure and record the actual peak overpressure. The measured actual peak overpressure Δ is then collected. P and the corresponding total charge Q equivalent area S、 Distance of the air shock wave from the explosion source R and minimum resistance line length L Then, according to equation (12) and using these data (Δ) P , Q , S, R, L The optimal coefficients are obtained by nonlinear fitting. k , α , η ).

[0039] (12) Step 4: Construct and validate the blast shock wave prediction model. First, establish a prediction model using the parameters obtained in Step 3. Second, install high-precision pressure sensors at the predicted measurement points (or representative locations) to simultaneously monitor the peak overpressure of the actual air shock wave generated by the blast. Then, compare and analyze the model's predicted values ​​with the actual measured values ​​on site and calculate the relative error. If the prediction error is within an acceptable range, it indicates that the coefficients are applicable and the model is reliable. If the prediction error is large or there is a systematic deviation, it is necessary to check the parameter acquisition (especially...). Q, S, R, L To determine if the data is accurate, the input parameters are corrected based on the analysis results, or the fitting coefficients are iteratively optimized and updated using newly added measured data.

[0040] Step 5: Establish a fitting coefficient database. For common tunnel cross-section types (such as archway, circular, and horseshoe-shaped), commonly used explosive types, and typical burial depth conditions, a fitting coefficient database can be established in advance through steps 1-4. During implementation, the closest coefficient set can be retrieved from the database based on the tunnel type and explosive type of the current project.

[0041] Step 6: Model Promotion and Batch Application. After verification and reliability, for subsequent sections of the same tunnel or similar cross-sections and blasting designs with similar explosive charges, only new data needs to be collected. Q , S , R With the parameters, the peak value of the shock wave at different locations can be quickly predicted using the calibrated formula (12) and coefficients, without the need for complex modeling or calculation. The fully validated model coefficients ( k , α , η The database includes the scope of application and can be directly promoted and applied in similar projects (similar geology, cross-section, explosives, burial depth), greatly improving the efficiency and reliability of safety pre-control of blasting shock waves in similar tunnels.

[0042] Example 2: To further illustrate the technical solution of this invention, the following example of full-section blasting of a highway tunnel is used to explain the specific implementation method of this invention. This method can be widely applied to tunnel blasting projects in railways, highways, water conservancy, hydropower, and urban underground spaces.

[0043] 1. Parameter Acquisition: Determine the total charge amount for single-stage detonation based on the blasting design. Q It weighs 48 kg; the equivalent area of ​​the tunnel at the site was calculated. S The minimum resistance line of the cut hole in the field blasting test is 14 m². L =1.2 m. At different distances from the explosion source R Measurement points were set up at the location, and a Minimate Pro4 vibration and air overpressure monitor was used to monitor the air shock wave overpressure Δ. P The overpressure data at different measuring points were classified and recorded.

[0044] 2. Coefficient calculation and application model establishment: such as Figure 1 As shown, the monitored overpressure data is plotted into an image, where the X-axis is... Q · R -1 S -1 The Y-axis is L / R The Z-axis represents the overpressure Δ P (10 5 Pa). Using formula (12) for Figure 1 The relevant model coefficients are obtained by fitting the graphical data points in the graph. k , α , η ), k =22.5, α =2.74, η =-0.95. This gives us the air overpressure prediction model for the tunnel, as shown in the following equation: ; 3. Model Validation: A measuring point was set up 30 m away from the explosion source. The measured peak air overpressure was 120.026 kPa. Using the air overpressure prediction model calculated in step 2 above, the predicted value was 125.639 kPa. The error between the result calculated by the prediction model and the actual measured result was 4.67%.

[0045] 4. Comparison and Effects: For example Figure 2 and Figure 3 As shown, the results predicted by traditional empirical formulas (1) and (2) have a large error compared to the measured data. However, the overpressure value calculated by the improved prediction formula is closer to the actual measured air overpressure value, and the prediction accuracy is significantly improved. This fully demonstrates the introduction of resistance lines in this invention. L Subsequently, the accuracy of predicting the propagation law of shock waves inside the tunnel was significantly improved.

[0046] The foregoing has illustrated the basic process and fundamental principles of this invention, as well as its advantages. Those skilled in the art should understand that this invention is not limited to the above embodiments. Any substitutions or variations that can be easily conceived without departing from the spirit and scope of this invention should be included within its protection scope.

Claims

1. A method for predicting the peak value of air shock waves in tunnel blasting based on the blasting action index, characterized in that, Includes the following steps: Step 1, Collection of explosive parameters and on-site information: Collect the parameters of the explosives used and on-site information during the blasting process; Step 2, Determining environmental parameters: Determine the environmental parameters during the blasting process; Step 3, obtaining coefficients: For different tunnel cross sections, different types of explosives, and different burial depths, small-scale field tests are first conducted to calibrate the parameters. Step 4: Construct and validate the blast shock wave prediction model; Step 5: Establish a database of fitting coefficients; Step 6: Model promotion and batch application.

2. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 1, characterized in that, Step 1 specifically includes: Step 1.1: Determine the total charge amount for single-stage detonation based on the blasting design. Q ; Step 1.2: Measure or calculate the cross-sectional area of ​​the tunnel in the area to be blasted based on the design drawings; for irregular cross-sections, calculate the equivalent area using the equivalent circle method or numerical integration method. S ; Step 1.3: Measure the linear spatial distance between the measuring point and the geometric center of the detonating charge. R ; Step 1.4: Measure or determine, based on the blasting design drawings, the shortest distance from the center of the explosive charge that contributes the most to the shock wave at the measuring point to the nearest free surface, i.e. L value.

3. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 2, characterized in that, Step 2 specifically includes: Step 2.1: Determine the initial air pressure based on altitude. P 0; Step 2.2: Determine the initial air density based on temperature and air pressure. ρ 0.

4. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 3, characterized in that, Step 3 specifically includes: Step 3.1: Before each test, set up multiple measuring points at different locations, install pressure sensors, measure and record the actual peak overpressure; Step 3.2, after collecting the actual peak overpressure Δ measured each time... P and the corresponding total charge Q equivalent area S、 The distance of the air shock wave from the explosion source R and minimum resistance line length L Then, according to equation (12) and using these data: Δ P , Q , S、 R, L The optimal coefficients are obtained by nonlinear fitting: k , α , η ; ；（12）。 5. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 4, characterized in that, Step 4 specifically includes: Step 4.1: First, use the parameters obtained in Step 3 to build a prediction model; Step 4.2 Next, install high-precision pressure sensors at the predicted measurement points or representative locations to simultaneously monitor the peak overpressure of the actual air shock wave generated by the blast. Step 4.3: Next, compare and analyze the model's predicted values ​​with the actual measured values ​​and calculate the relative error. If the prediction error is within an acceptable range, it indicates that the coefficients are applicable and the model is reliable. If the prediction error is large or there is a systematic bias, the parameter acquisition needs to be checked. Q, S, R, L To determine the accuracy, the input parameters are then adjusted based on the analysis results, or the fitting coefficients are iteratively optimized and updated using newly added measured data.

6. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 5, characterized in that, Step 5 specifically includes: For common tunnel cross-section types, commonly used explosive types and typical burial depth conditions, a database of fitting coefficients is established in advance through steps 1 to 4. During implementation, the closest coefficient set is retrieved from the database based on the tunnel type and explosive type of the current project.

7. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 6, characterized in that, Common tunnel cross-section types include archway-shaped, circular, and horseshoe-shaped.

8. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 7, characterized in that, Step 6 specifically includes: Once verified as reliable, for subsequent sections of the same tunnel or similar cross-sections and blasting designs with similar explosive charges, only new samples need to be collected. Q , S , R With the parameters, the peak value of the shock wave at different locations can be quickly predicted using the calibrated formula (12) and coefficients, without the need for complex modeling or calculation; The fully validated model coefficients k , α , η The scope of application is included in the database, and it can be directly promoted and applied in similar projects, which will greatly improve the efficiency and reliability of safety pre-control of blasting shock waves in similar tunnels.

9. The method for predicting the peak value of air shock wave in tunnel blasting based on the blasting action index according to claim 8, characterized in that, Similar projects include geology, cross-section, explosives, and burial depth.

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